Osteohistological signal from the smallest known phytosaur femur reveals slow growth and new insights into the evolution of growth in Archosauria.

Fossils of embryonic and hatchling individuals can provide invaluable insight into the evolution of prenatal morphologies, heterochronies, and allometric trajectories within Archosauria but are exceptionally rare in the Triassic fossil record, obscuring a critical aspect of archosaurian biology during their evolutionary origins. Microvertebrate sampling at a single bonebed in the Upper Triassic Chinle Formation within Petrified Forest National Park has yielded diminutive archosauriform femora (PEFO 45274, PEFO 45199) with estimated and measured femoral lengths of ~31 mm and ~ 37 mm, respectively. These new specimens provide the unique opportunity to assess the preservation, body size, and growth dynamics of skeletally immature archosauriforms in North America and compare the growth dynamics of archosauromorphs within an evolutionary and ontogenetic context.

A small venomous reptile from the Late Triassic (Norian) of the southwestern United States.

Reptile feeding strategies encompass a wide variety of diets and accompanying diversity in methods for subduing prey. One such strategy, the use of venom for prey capture, is found in living reptile clades like helodermatid (beaded) lizards and some groups of snakes, and venom secreting glands are also present in some monitor lizards and iguanians. The fossil record of some of these groups shows strong evidence for venom use, and this feeding strategy also has been hypothesized for a variety of extinct reptiles (.

Triassic stem caecilian supports dissorophoid origin of living amphibians.

Living amphibians (Lissamphibia) include frogs and salamanders (Batrachia) and the limbless worm-like caecilians (Gymnophiona). The estimated Palaeozoic era gymnophionan-batrachian molecular divergence suggests a major gap in the record of crown lissamphibians prior to their earliest fossil occurrences in the Triassic period. Recent studies find a monophyletic Batrachia within dissorophoid temnospondyls, but the absence of pre-Jurassic period caecilian fossils has made their relationships to batrachians and affinities to Palaeozoic tetrapods controversial.

A new non-mammalian eucynodont from the Chinle Formation (Triassic: Norian), and implications for the early Mesozoic equatorial cynodont record.

The Upper Triassic tetrapod fossil record of North America features a pronounced discrepancy between the assemblages of present-day Virginia and North Carolina relative to those of the American Southwest. While both are typified by large-bodied archosaurian reptiles like phytosaurs and aetosaurs, the latter notably lacks substantial representation of mammal relatives, including cynodonts. Recently collected non-mammalian eucynodontian jaws from the middle Norian Blue Mesa Member of the Chinle Formation in northeastern Arizona shed light on the Triassic cynodont record from western equatorial Pangaea.

The earliest equatorial record of frogs from the Late Triassic of Arizona.

Crown-group frogs (Anura) originated over 200 Ma according to molecular phylogenetic analyses, though only a few fossils from high latitudes chronicle the first approximately 60 Myr of frog evolution and distribution. We report fossils that represent both the first Late Triassic and the earliest equatorial record of Salientia, the group that includes stem and crown-frogs. These small fossils consist of complete and partial ilia with anteriorly directed, elongate and distally hollow iliac blades.